It is known that a ship's hull friction resistance in water will be decreased by supplying air bubbles to the moving hull's surface.
As a means to send air to the micro bubble generator located in the ship's bottom (lateral surface), Prior Art 1 describes how air is sent into an air tank from blower. The air is retained in a compressed state, and through a pipe attached along the side outside of the hull, the air that is accumulated is supplied to the bubble forming region.
Prior Art 2 describes how air is supplied in the bubble genesis region through a pipe attached along the side outside the hull from a gas feed means provided on the deck.
It is required that micro air bubble diameter should be small as possible. For this purpose, Prior Art 3 describes how such micro-bubbles can be generated according to the Kelvin-Helmholtz-Instability phenomenon.
Namely, in Prior Art 3, a recess in the shell (immersion surface) of a ship's bottom is prepared, a gas inlet tube is connected with the recess to supply air, and a wedge-shaped negative pressure formation part is attached to the upper stream side of the recess to then generate micro-bubble in a recess to effect the Kelvin-Helmholtz-Instability phenomenon.
Moreover, Prior Art 4, describes the technology of employing a wing as a means for which to make micro-bubbles instead of the wedge-shaped negative pressure formation part of Prior Art 3. Particularly, blower 35 is disclosed in FIG. 17A, 17B of Prior Art 4, and the air is supplied from the blower 35 in a fluid passage is described in column 23 and 24 of Prior Art 4.